Re: Help with `92 SC2 - Random Stalls, No Hot Starts, High RPMs on Start

Quote:

Originally Posted by WesAlvaro

Big news, but first a reply:

Ok, well, if the PCM doesn't prevent the fan from running at high speed then maybe it was just timed well with me slowing down.

Most likely.

Anyway, the fan does operate when jumping the two terminals. I think I'll also be doing the manual fan switch mod once we get this thing running.

If the fan runs when jumping the 2 terminals in the ALDL connector then its fine and you are just being jumpy about the gauge. The fan will not turn its self on until the pointer is AT the red. Just relax and let auto do it.

The only code flashing was 12, so no more info there.

I was only looking for the FAN test part of it. OBD-1 does not store codes unless the light is on.

I'll be waiting to see what's up with the A/C before bypassing the pressure switch since I checked the switch and it's probably right, there's no refrigerant in there. I'll be getting some 143 with dye and loaning that leak checker from AutoZone at some point...

Do not use any stop leak in that system as it will ruin the TXV(thermal expansion valve) and do not put in more than 2 cans of gas as that is a full charge. Be sure that he caps are installed on both charging fittings or you will have a leak. Do not run the compressor without gas AND cold air. No cold air means no oil circulation and you will burn up the compressor. I realize $$ is tight so you are forced to do this yourself.

So I took off the air filter from the throttle body and stuck my finger on the air intake for the IAC. I was able to bring the RPMs down to a managable level and then (we'd been afraid to let it idle that hard for that long, while still increasing! ) it actually regulated itself and calmed down to a normal idle! What does that mean?!?!

That means you have located the problem probably. There are 2 possibilities here. First step is to properly adjust the throttle stop screw. It's on the side of the throttle body. With the car warmed up you block that IAC port completely and adjust the stop screw for 450 to 550 RPM. You have to get it down to that RPM band. Then see if the IAC is capable of controlling the RPM properly. If not its time to go to the junk yard and buy another IAC. That will be both cheaper and get you a better part. You can probably clean a used one if careful. Clean off the pintle and its seat in the throttle body and clean out the inside of teh IAC with nothing but CRC Electrical Connection cleaner. Any other solvent will ruin the stepper motors inside of it. Once clean ed and dry put it all back together and see if it works now. You can go to RockAuto and see which years have the same IAC, or ask.

We tried that a few times and it kept starting back up strong, I was able to get the RPMs down and then it normalized.

In other news, I fiddled with putting the air filter back on and cleaning up. I closed the hood and decided that I would see what would happen.

It didn't start!

It turned over fine, but it didn't start! There was food on the table, so I couldn't mess with it anymore, but this seems to me like the CKS is getting hot and opening up.

Hopefully, if it's this easy to recreate, I'll try it again tomorrow and test for a spark with a spare plug or should I just take the wires off the 1&4 coil like richpin does in a video?

So, what do you think is causing the high RPMs, now?

And what do you think would be causing it not to start after it starts fine a few times?

THANK YOU SO MUCH AGAIN!

The failure to start when hot could be the setting of the stop screw. Once its fixed then move on to the CKP. Swat one bug at a time or you go nuts.

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Re: Help with `92 SC2 - Random Stalls, No Hot Starts, High RPMs on Start

Adjust slowly and the engine will not die. If you can not establish a 450->550 idle then there is a vacuum leak into the manifold. Once you establish the port blocked minimum idle slowly remove your finger from the port. The rpm should increase to the normal idle and stabilize. If it continues to increase above the nominal 850 then the IAC is not stepping or is stuck or the port in the throttle body is blocked with carbon. When you totally close off the port if the engine dies then adjust the stop to hold 500 rpm+/- as you block it off. It is likely that you will find you need a can of the CRC Electrical Connection cleaner to revive the IAC. May have to re-clean the IAC port in the TB also. The important area is the port where the pintle seats to contro0l idle air flow.

Don't try and battery check the IAC. It is a digital pulse stepped motor.

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Alright, so I was unable to get the car to idle with the IAC port closed. Who knows if the IAC is bad or not, it actually seems fine considering I was choking the thing, it recovered well a few times...

I even pushed in the throttle screw a bit and it raised the RPMs as expected, but I still wasn't able to close off the IAC port.

After trying a few times, the no-start problem showed up again. So diagnostics on a running engine ceased.

So does this conclude that I just have (a hidden) vacuum leak?

Or could this be anything else at all?

Is there only one kind of vacuum leak? Can one narrow down that search at all or am I just going to be spraying stuff around my engine until I find it?

On another note, I don't think the no-start thing is related to this problem. We ran the car for a few minutes, first turnover, no problems. And then, after the car warmed up. Absolutely no start. Starter was turning strong, but no ignition. What do you think?

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Re: Help with `92 SC2 - Random Stalls, No Hot Starts, High RPMs on Start

Get the engine to its fully warmed up condition (ects replaced, thermostat replaced, coolant temperature indicating 3/8ths - between the 1/4 and 1/2 mark) and whatever is now idling smoothly. With the engine off remove the intake air tube to access the throttle body and start up the engine; simply cover the bypass air port in front of the throttle plate with tape and one of two things will occur - the engine shuts off or idles above 600 rpm. Idling above 600rpm means adjusting the throttle stop screw to 500-600rpm. The engine dying or running below 500rpm needs the throttle stop screw adjusted to open the throttle plate so the idle runs 500-600rpm. That's it. Get the low speed idle by adjusting the throttle stop screw for 500-600rpm. With this done, removing the taped over bypass air port will immediately raise engine rpm momentarily until the pcm catches on and automatically reduce rpm back to 800-900. The idle air control valve (iacv) is now taking over idle speed function as monitored by the pcm. If the iacv was never meddled with then you should have a near perfect idle that was missing from a worn out fuel pump leaning out fuel mixtures.

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Let the car idle till it is at normal temp, 3/8 on the gauge 96 and newer models or 1/2 on 95 and older. Then slowly block the IAC port and adjust screw to hold 450->550RPM when the port is fully blocked off. While blocking it off if the car drops down too low turn the screw to open the throttle plate a bit. If it slowly dies but is trying to run at 500+/- that is OK also. With good plugs it will usually idle right down to 500 and not stall out with no problem though. The throttle body will be hot so be sure that you have a big chunk of leather belt to block the port with. Do not try tape or paper as it will end up in the engine. Piece of old leather belt will not get sucked in and will keep you from burning your finger.

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